A number of medicines for treatment of a variety of diseases contain, as active principle, naturally occurring peptides or their synthetic analogues.
Because of the instability of small and medium size peptides, particularly vasopressin, oxytocin, and their analogues, in the environment of the gastrointestinal tract their uptake, when given as a medicine or for similar reasons, is still very unsatisfactory. Thus, better delivery systems for non-parenteral, particularly for oral, administration of peptides and their analogues are desirable, cf. Davies, S.: "Developing delivery systems for peptides and proteins", Scrip Magazine 1992, 34-38.